Electrical terminal



NOV. 21, 1933. 1 RlCHTER 1,935,818 I ELECTRICAL TERMINAL Filed May 17,1932 lNVENTOR Patented Nov. 21, 1933 UNITED STATES PATENT OFF ICEApplication May 17, 1932.

3 Claims.

My invention relates generally to terminals for circuit elements and, asherein embodied, is specially designed for use with high resistanceunits. In order to meet trade requirements, the efforts 5 ofmanufacturers of high resistance units, particularly of the wire-woundtype, have been directed towards increasing the resistance value of theunit to the highest possible point while, at the same time, decreasingits overall dimensions.

This has led to the use of extremely fine, closely wound resistancewire, which has so little body,

it will not withstand the heat of a soldering iron and, in consequence,connection between ends of the resistance wire and the terminals of theunit usually have to be made by some form of clamp.

In a well known resistance unit or resistor, which has been extensivelyused in the art, the clamp employed is formed of a single length of abinding wire, a number of turns of which are first wound on the body orinsulation covering of the unit, as an anchorage winding, then anadditional number of turns are wound on the exposed end of the coiledresistance wire, as a contact winding and beyond that, a short length ofthe binding wire is extended outward to serve as the terminal proper.

This wire clamp terminal, while generally satisfactory, has a seriousmechanical structural defect, which the present invention is designed toremedy. It has been found that when the wire clamp terminal is subjectedto longitudinal strain or a pull, as frequently happens, the contactwinding will loosen and unwind, badly or destroying the contact andrendering the unit unfit for further use.

In order to prevent such strain on the wire clamp tending to cause it toloosen and lmwind, as above described, I form the winding and theterminal proper of separate lengths of wire and so relatively arrangethem that any longitudinal strain or pull to which the terminal propermay be subjected, will have no eflect in creating an unwinding tendencyof either the contact or the anchorage winding and such windings will bemaintained tight and secure, thereby incurring good contact with theresistance wire.

A construction suitable for carrying my invention into efiect isillustrated in the accompanying drawing, in which- Fig. 1 is a view inelevation showing my improved terminal applied to a resistor;

Fig. 2 is a longitudinal section through one of the terminals of theresistor, before it is completed by being solder-dipped;

Serial No. 611,801

Fig. 3 shows the efiect of solder-dipping the terminal to complete it,and

Fig. 4 illustrates a modification.

Referring now to the drawing, 1 represents a well known form ofresistance unit in which a very fine resistance wire 2, is spirally andclosely wound on a core of asbestos or any other suitable material 3,and enclosed, excepting the ends 4, 4, in a covering of insulation 5.

At each end of the resistance unit a terminal is formed by arranging ashort, straight length of comparatively heavy gauge wire 6, inoverlapping relation with the end of the unit and securely clamping itin position by a winding of binding wire 7. The overlap of the terminalwire 6, extends beyond the exposed end 4 of' the resistance unit and onto the insulation covering 5, so that the first six or eight turns ofthe binding wire serve as an anchorage winding, in clamping the terminalwire to the body of the unit, while the remaining turns, over theexposed end of the unit, form a contact in clamping the terminal wire inclose relation with the resistance wire.

Thus constructed and arranged, strain or pull onthe terminal wire willhave no tendency to unwind either the anchorage or the contact winding,so that unless the terminal wire is pulled completely out of the grip ofboth windings, which is practically an impossibility, good con- 85 tactbetween the terminal and the resistance unit will be assured.

To further strengthen the terminal and give it a more finishedappearance, I solder-dip it to a depth, including the binding wire andso securely unite the turns against loosening or In showing my improvedterminal applied to the particular resistance unit above described, I donot wish to be understood as intending to limit myself to the same, asit will be apparent that the terminal may be applied with equaladvantage to other and different units without material, if anymodification.

As will be apparent, the gauge of the wire and the number of turns inboth the contact winding and the anchorage winding, may be varied tomeet the requirements of the,particular form or type of unit to whichthe terminal is applied, the showing in the drawing being illustrativeonly and not intended as an accurate guide for practical construction.

Among the most important advantages of the invention may be mentionedthe exceptional strengthof theterminal inwithstandingexcessivelongitudinal strain, without disturbing, weakening or otherwiseimpairing contact with the very fine resistance wire and the arrangementfor imparting to the terminal this effective contact protection, that isto say, the location of the contact winding between a strong anchoragewinding on the body of the unit and the terminal proper, to which thestrain is applied.

As a further means of strengthening the terminal, I may modify theconstruction, as shown, in Fig. 4, in which a stranded wire 6 isemployed instead 'of a single wire and the overlapoing ends spread apartunder the clamping action of the anchorage winding.

Having thus described my invention, what I claim is:

l. A resistor consisting of a resistance wire spirally wound on asuitable core and enclosed, excepting the ends, in a covering ofinsulation, a terminal reinforcement in the form of a straight length ofwire having one end exteriorly arranged in overlapping contact relation,with the exposed end of the coiled resistance wire, and a winding ofbinding wire securing the overlapping members together in close contactand forming an enclosing sheath for the same and the adjoining portionof the insulation covering.

2. A resistor consisting of a resistance wire spirally wound on asuitable core and enclosed, excepting the ends, in a covering ofinsulation, a terminal reinforcement in the form of a straight length ofwire having one end exteriorly arranged in overlapping contact relationwith both the exposed end of the coiled resistance wire .and a portionof the insulation covering, and a winding of binding wire securing theoverlapping members together in close contact and forming an enclosingsheath for the same.

3. A resistor consisting of a resistance wire spirally wound on asuitable core and enclosed, excepting the ends, in a covering ofinsulation, 2. terminal reinforcement in the form of a straight lengthof wire having one end exteriorly arranged in overlapping contactrelation with both the exposed end of the coiled resistance wire and aportion of the insulation covering, and a winding of binding wiresecuring the overlapping members together in close contact and formingan enclosing sheath for the same, the said sheath being solder-dipped tounite the turns of the winding.

HENRY G. RICHTER.

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